1. Field of the Invention
The present invention concerns a method and a device for manufacturing corrugated board or the like.
2. Discussion of the Related Art
It is known that the production of corrugated board takes place in different steps. Single corrugated board, which normally consists of a corrugated intermediate layer which is glued between two outer layers, is produced for example by providing a waveform to the material for the intermediate layer in a first step and by subsequently gluing the material for the outer layers on both sides of it. The material for forming the above-mentioned layers is hereby continuously supplied in the shape of material strips. First, a first outer layer is glued onto one side of the corrugated intermediate layer, and then the second outer layer onto the other side. As material strips with glue in between are joined together, the material strips have to be pressed well together in order to obtain a good bond. To this end, the material strips are guided along different parts of a device to provide the glue on the one hand and to compress the material strips on the other hand.
When the first outer layer is fastened to the corrugated intermediate layer, this intermediate layer can still be supported at its free side, for example by means of a supporting roller with a corrugated surface. Afterwards, an outer layer will also have to be provided on the other side of the intermediate layer. However, this is not as simple as in the first step, since the corrugation of the intermediate layer can no longer be supported now, so that any pressing on will have to be done with some care in order to prevent the corrugated intermediate layer and any possible outer layers from being flattened and/or damaged.
When producing corrugated board, it is also important to make sure that, on the free side of the corrugated board covered on one side, all the wave tops are entirely covered with glue, such that the second outer layer can be fastened well.
A device is known from U.S. Pat. No. 5,129,980 whereby use is made of press-on shoes to press the corrugated board covered on one side against a glue roll. The press-on shoes are hereby fixed to a frame in a pivoting manner, and a spring is situated between every press-on shoe and the frame, such that the corrugated board covered on one side is pressed against the glue roll.
Further, every press-on shoe is provided with an adjusting screw which is to guarantee a minimum distance between the glue roll and the press-on shoe concerned when cardboard is no longer available, in order to avoid that, when the cardboard comes out, the press-on shoe would make contact with the glue roll, as a result of which glue would end up on the press-on shoe and the glue roll could be damaged.
A disadvantage of this known embodiment consists in that the above-mentioned springs, as they are movable and deformable elements, may jam, or in other words get locked. Also, frictional forces may be created between said spring and the guide around which this spring is usually provided.
Moreover, such friction causes wear, as a result of which cracks and the like may occur. Due to said wear, as well as due to the vibrations which are generated in such a spring, it will also be subject to ageing. Because of the aforesaid friction, which is often variable, and as a result of the above-mentioned other factors, it is often difficult to ensure a permanent press-on force, which often has a negative effect on the quality of the produced end product. For an irregular pressing-on may result in an irregular gluing and a bad bonding, as well as to unwanted impression marks in the cardboard.
Further., the use of springs requires a regular maintenance.